While still early, publishers are starting to gauge how beneficial posting fast-loading content directly to Facebook via Instant Articles can be to them, both in terms of traffic performance and revenue. Views in the U.K. are mixed.

All the major U.K. publishers are publishing to Instant Articles to greater or lesser extents. The BBC and the Guardian were among the first, with the Guardian in particular going all in. The Economist, Financial Times, The Sun, Trinity Mirror, Daily Mail, Business Insider U.K., among others, are all testing it.

Trinity Mirror is a fan. The publisher runs all content for its biggest newspapers (The Mirror, Manchester Evening News) via Instant Articles and wants the same for its smaller titles. Trinity Mirror strategy director Piers North said the additional international reach the publication has gained is paying off, although he wouldn’t reveal specifics. Revenue-wise, it’s a money-making proposition, he added.

“We’re putting tens of millions of impressions down Instant Articles. At the moment, we see no reason to throttle that. The money it’s making us isn’t insignificant,” said North.

Publishers like The Independent have said that yields on Instant Articles have eroded over the last few months, even for video. But that’s not a universal view. Several publishers have said that their own yields have remained stable, North among them. Currently, Facebook sells the ads for Trinity Mirror via its Audience Network; however, in the future, the publisher plans to take that in-house.

French newspaper Libération is also content with its progress. It has been monitoring how long people spend on Instant Articles and found it has double (4 minutes 48 seconds) the time spent on its own mobile site.

The revenue is improving too. In February, the CPM was $1.30. In the summer, it rose to $3.40; now, it’s back down to $2.10 — double the Instant Articles ad revenue it made last year, when it pulled in around €10,000 ($11,200). On its own mobile sites, CPM is less than $1.

Not everyone, however, is seeing the same success with yields. The commercial chief of a major digital media publisher, who wished to stay anonymous, likened the yields on Instant Articles to the equivalent of remnant inventory traded programmatically.

Ramp up or pull backMany U.K. publishers remain cautious. In April, an anonymous analytics company reported that publishers were seeing Facebook referral traffic drop, and those going big on Instant Articles were hit hardest. Some are therefore just testing a handful of articles a day on Instant Articles, which is possibly why their revenue isn’t higher. Some, like Business Insider U.K., are aggressively testing whether they need to ramp up or pull back on how much content they publish via Instant Articles, so as to reach a decision by the end of the year.

Others are wary of audience cannibalization. “We tease it for sharing capabilities rather than thinking of it as a way to make more money,” said one commercial publishing exec, who wished to remain anonymous. “We don’t want to cannibalize our own audiences, and I won’t be pushing the editorial teams to run more content through it because then you’re on the crack pipe.”

Instant Articles should be used to attract new audiences, but it’s not that easy to see if a new person is reading it, because that information is in Facebook’s ecosystem, not yours. You can only assume, they added.

Cherry on the cakeSeveral publishers told Digiday that revenue they’re making from Instant Articles is in the range of “tens of thousands” of pounds a month. “It’s pennies not pounds,” said one publishing exec.

That said, additional revenue is good, as long as it’s kept in perspective. “You make money from it, but it shouldn’t be seen as a main revenue stream,” said Simon Haynes, digital director at Northern & Shell, which owns the Daily Star and Daily Express tabloid newspapers. “Anything you make should be a nice surprise, like a cherry on the cake, nothing more. If you make it a core part of your revenue makeup, you’re submitting to the will of Facebook.”

Despite the promise of Instant Articles, in speeding up page load times for publishers, and helping widen international reach, it’s not for everyone. A national newspaper commercial exec, who wished to remain anonymous, said it’s not been blown away by the results. “Every time you make a change to anything you do, it costs money in your product team, so we wanted to get live with it and then monitor the traffic, to assess if it’s worth continuing with or increasing it. But we’ve not yet seen sufficient traffic increases to justify investing in it any further,” the exec said.

Other, more niche players like auto magazine Car Throttle, has already bowed out of using Instant Articles after running their own brief trials. Throttle ran all its content for one week on Instant Articles in March and saw pageviews drop 16 percent to 3.3 million.